I'm wordering how powerfull shell scripting really is...

Like is it possible to perform the following task from out of a shell script ???

telnet some.machine.com;
enter user_id;
enter password;
execute some_command;
exit;

I tried just echoing the user id and password but after the telnet line my script wa waiting for input, and didn't carry on with the script :(

Shell scripting is very powerful and in your case most of what you would like to accomplish would be done by telnet it self, without the need of making a script. Read the man-page of telnet (man telnet).

To execute a command in telnet you probably would use > or < to redirect in-/output to telnet. (Might be the wrong order of > and <).